||This invention relates to avariable aperture coding/decoding systm for use in a spread specturm system provides multiple phase coding of a input NRZ bitstream.Each bit of a coded output signal is coded to encompass a predetermined different number of clock periods depending on the logic level of the input signal. A coded bit exhibits a predetermined reference number of clock periods,eg.,9,when the input signal does not exhibit a logic level transiction. When the input signal exhibits a phase change from a 0 to a 1 logic level,the bit width of an associated coded bit is increased by 1 clock period,to 10 clock periods. When the input signal exhibits a phase change from a 1to a0 logic level,the bit width of an associated coded bit is decreased by 1clock period, to 8 clockperiods. Thus the coded output signal may contain three types of information represented by a bit width change proportional to predetermined factor N.